The initial situation and the object of the invention is best illustrated on the example of a state of the art mobile network. However, similarities and an equivalent applicability of the invention to other, e.g. fixed line or wireline access networks are easily comprehensible.
FIG. 1 shows a (simplified) principal architecture of a fourth generation (4G) mobile network. User terminals (UE) are connected via a radio access network (RAN) comprising eNodeB base stations, through an evolved packet core (EPC), to service endpoints in a service delivery network (SDN), which most often is represented by server farms, where content and services are stored and/or made available for UE access. In this application, an SDN may represent a mobile network operator (MNO) service network, or a service network of a third party service provider, or the Internet, or any other kind of network providing services or access to services. The EPC mainly comprises gateways, e.g. serving gateways (S-GW) which mediate UE traffic from the base stations towards packet data network gateways (P-GW), which act as transition points to SDN or other networks. The involvement of eNodeB, S-GW and P-GW is to a certain extent steered by a mobility management entity (MME). Besides end-to-end (E2E) data, which should be exchanged between both peer ends (UE/SDN), denoted as U-plane further on and in FIG. 1 shown in bold lines, there is a significant exchange of mobile network control messages between nodes of the mobile network, which are not necessarily related to the services themselves (payload), but which are necessary to run and ensure an E2E service delivery with mobile users. This information exchange, denoted as C-plane further on and shown in dotted lines in FIG. 1, comprises e.g. measurement reports from UE to eNodeB and MME, user/service related information between UE and a P-GW, tunnel setup information between S-GW and P-GW, user authentication and authorization between home subscriber server (HSS) or home location register (HLR) and a variety of nodes. Note that this information is not to be mistaken with control messages between services and user devices (like HTTP or FTP), which are considered to belong to a higher layer, and that this information is in no way related to control messages of underlying transport nodes. In FIG. 1, nodes having control functionality are indicated with a C-triangle, those having data forwarding functionality are marked with a D-circle, and of course, some nodes may have both functionalities. Note, that all entities, even if shown only once in FIG. 1, may appear in multiple instances within a related network.
With respect to transport, there is most often a clear separation between RAN and EPC. Base stations may be far from each other in rural environments and densely co-located in urban areas. Thus, operators do have to cooperate and often have to rely on third party transport, when they do not own a transport network in a certain area (e.g. in rural areas).
RAN transport usually covers the radio section of the access area and a potential first level of aggregation between base stations, their potentially common control and the transition to the EPC. Related transmission technologies may use any kind of media, including e.g. wires, fibers or air (microwaves), combined with any suitable mechanisms and/or protocols like e.g. DSL, Ethernet, IP, etc. Optical systems like passive optical networks (PON) offer attractive solutions for aggregation bandwidth sharing, and future WDM based PONs, also referred to as next generation optical access (NGOA), as disclosed with WO2011/067350 A1, enable virtually unlimited transmission bandwidth for each base station and user.
The EPC typically provides e.g. further levels of aggregation, user authentication, service invocation including mobility management, and routing and switching of information between users and service providers. It usually employs long haul optical transmission based on ring and mesh structures with DWDM and MPLS/GMPLS technologies. Cross connect and router functions are typically used for interconnecting the RAN with the EPC. S-GWs and P-GWs are typically placed in the transition areas between RAN and EPC and EPC and SDN in order to deal with disruptions in related transport technologies.
New concepts like network virtualization and OpenFlow have introduced new capabilities in the way of operating, controlling and managing telecommunication networks. Network virtualization enables the separation and isolation of distinctive networking resources from a physical network infrastructure and to use them to form virtual networks, which are completely independent of each other (see e.g. PCT/EP2010/066534). OpenFlow advocates the separation of the control (C-plane) and the forwarding plane (U-plane) of switches and routers so as to form simple and high performant forwarding machines to be controlled by a highly flexible and efficient control system (see www.openflow.org).
According to the above concept, commercial-off-the-shelf routing and switching platforms are (re-)used. In a simplified view, those already comprise facilities as shown in FIG. 2 for data path handling (e.g. a switching matrix), related control software and flow tables, which define how data packets are handled (routed, switched) depending e.g. on the information that is contained in the packet headers. A simple rule could for example mean that incoming packets on port 0 will be forwarded to port 2, if the destination address found in the header can be resolved, and to port 3 otherwise.
The approach that OpenFlow brings to this system is that the flow tables can be manipulated from outside of the device via an application programming interface API (OpenFlow handler/interface) and that a control instance can slice different resources from the device and present those, or a subset of those, to further control instances outside of the device (FlowVisor). This way an application can manipulate resources of e.g. a group of Ethernet switch(es) by manipulating a virtual flow table, which is representing an instance, which appears as a single switch or a FlowVisor instance, hiding a hierarchical structure comprising of switches and/or further FlowVisor controllers behind it. The application doesn't need to have the knowledge of whether its access to resources directly affects a physical switch or a virtual switch formed by several switches, which may e.g. be hierarchically organized.
Transport for 4th generation and beyond mobile networks will advantageously use fiber based infrastructures. PON based systems or point-to-point solutions can be used in the access as illustrated in FIG. 3. WDM rings may be used for further aggregation and DWDM is the solution for the long haul. However, for each operator, the network and the combination of the components may be different. Also upgrade scenarios with SDH or Sonet rings as installed today will still be used in the future. Multi-generation RANs (combinations of 2G, 3G and 4G technologies) will add to the diversity.
Due to the inhomogeneous transport layers (packet vs. SDH/TDM, fibre vs. copper vs. microwave) U-plane (user data) and C-plane (operator control data) are kept agnostic of the underlying transport technologies and are based on IP/MPLS or carrier Ethernet technologies (CET). As a consequence, there are a lot of transition points where e.g. optical or microwave radio access is interworked into optical Metro and/or long haul transport, each with conversion from one to another transport technology. At these conversion points electrical-optical or optical-electrical-optical (OEO) conversion is required, and most often IP/MPLS switches and routers are needed, each with high demands on performance and throughput, which require costly and energy consuming installations. Especially with the expected growth in bandwidth (estimated factor of 100 within the next 10 years) those neuralgic points in the network become more and more critical.
In the near future most likely all transport network interconnections will be fiber based and thus purely optical—but OEO conversions will still be necessary in the nodes, just to cope with the different transport technologies. This will impact the overall network architecture, its performance, and the related cost in an unbeneficial manner.
Todays network architectures and their related distribution of functions to nodes in a certain way reflect the capabilities and deficiencies of the transport networks. In many cases the IP layer is considered as some kind of a “convergence layer”. Whenever underlying technologies cannot be interworked properly on lower layers, the issue is solved by routing. This is perfectly reflected and illustrated by the multiplicity of different nodes to support the different functions in the 3G and 4G system architectures—and each of these nodes may mean an additional OEO conversion.
In the evolution of mobile networks, functionality has been moved around between network nodes to cope with new challenges (2G BTS and BSC became 3G NodeB and RNC with completely different function split) and exploitation of new transport capabilities. Still, the multiplicity of different nodes is still there. Even worse, the change in architecture requires significant investments in the networks in order to upgrade the network and its nodes with the functions required by each new architecture.
The complexity of the system further implies certain delays incurred by control information to be processed and passed through the nodes and to be exchanged between the nodes. This limits the performance and the throughput of the system for handling of e.g. communication requests, mobility support, protection switching, and many other control activities. Network growth and additional function upgrades even add to such issues.
A separation of C- and U-plane as proposed by OpenFlow would not solve the problems as the forwarding part of the nodes would still be in place and still require OEO conversion, electronic switching and forwarding, and exchange of control information in each node. In some cases such separation would even further reduce the performance due to additional delays incurred by moving around the control information between the locations of the forwarding functions and the related remote control entities.
Another frequently recommended and probably the most popular approach to deal with such problems is the attempt to offload certain nodes from certain traffic, that not really needs these nodes' functions. This implies the separation of related incoming traffic in the edge nodes in order to bypass other core functions on the way to its destination edge. Still, this has quite limited effects, due to still a significant number of conversions needed and an increase in control complexity.
It is thus an object of the invention to tackle the deficiencies, limitations and complexities as described above and to provide a solution that enables a more efficient and more performant conveyance of traffic in telecommunication networks.